This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art.
Cellulosic materials may be converted into valuable intermediates, which may be further processed into fuel components. As such, cellulosic materials are of considerable interest as feedstocks for the production of sustainable fuels and/or chemicals.
The combustible fuels and/or chemicals from biological sources, such as cellulosic materials, are often referred to as biofuels and/or biochemicals. The use of biological sources may allow for a more sustainable production of fuels and/or chemicals and more sustainable CO2 emissions that may help meet global CO2 emissions standards under the Kyoto protocol (i.e., may reduce greenhouse gas emissions).
Such biofuels can be used for blending with conventional petroleum derived fuels. Biofuels used for blending with conventional gasoline fuels include alcohols, in particular ethanol. Biofuels such as fatty acid methyl esters derived from rapeseed and palm oil can be blended with conventional diesel fuels. However, these biofuels are derived from edible feedstock and so compete with food production.
Biofuels derived from non-edible renewable feedstocks, such as cellulosic material, are becoming increasingly important, both economically and environmentally.
WO 2012/035410 describes biooils that can be derived, for example, from plants such as grasses, trees, wood chops, that can be dispersed in a hydrocarbon type liquid and subjected to a hydroreforming step. WO 2012/035410 indicates that such biooils may be obtained by thermochemical liquefaction, notably pyrolysis. It is indicated that a catalyst can be added to enhance the conversion in the so-called catalytic pyrolysis.
A process for liquefying a cellulosic material is described in WO 2011/141546 in which a cellulosic material such as wood is liquefied by contacting it simultaneously with an acid catalyst, water, a polar co-solvent, a source of hydrogen and a hydrogenation catalyst. The hydrogenation catalyst can comprise a heterogeneous or homogeneous catalyst. WO 2011/141546 indicates that if the hydrogenation catalyst is a heterogeneous catalyst, the catalyst preferably comprises a hydrogenation metal supported on a carrier. The heterogeneous catalyst and/or carrier may have any suitable form including the form of a mesoporous powder, granules or extrudates or a megaporous structure such as a foam, honeycomb, mesh or cloth. The heterogeneous catalyst may be present in a liquefaction reactor comprised in a fixed bed or ebullated bed or suspended slurry.
In liquefaction processes, deep removal of catalyst particles and/or catalyst fines from the liquefied product can add significantly to the costs of such processes. Moreover, the liquefied product may to some extent still remain contaminated with catalyst particles and/or fines, affecting its quality. The use of megaporous catalysts as described in WO 2011/141546 may reduce the need for such deep removal and may reduce the contamination with catalyst particles and/or fines in the liquefied product.
However, in order to obtain an economically interesting process, the degree of liquefaction may need to be further improved.
It would be an advancement in the art to provide a liquefaction process that allows one to reduce and/or avoid contamination of the liquefied product with catalyst particles whilst still obtaining a good degree of liquefaction of the cellulosic material.
Hence, there remains a continuing need for the development of improved processes for liquefying cellulosic material to produce liquefied products, especially fuel components and/or fuel component precursors for use in the preparation of biofuels.